Commercial food service establishments, such as restaurants, produce considerable amounts of organic material in their waste or drainage water which often includes high levels of grease or oil. Such materials can clog or adversely affect public wastewater and sewer systems. Most jurisdictions therefore require that such grease and oil be removed from the wastewater at the commercial establishment before it is permitted to enter the wastewater system.
To effect such removal, the commercial establishment will typically install a grease interceptor on its wastewater outlet line from its food preparation area, such as its kitchen. The purpose of the grease interceptor is to permit the free flow of wastewater, while capturing any grease or oils contained in the water. The process of grease interception involves the separating and retaining of globules of grease, fats and oils from wastewater as it passes through the grease interceptor. Typically the oily wastewater passes into the grease interceptor at one end and as the water flows through the interceptor it is slowed down, allowing the lighter than water components, such as grease and oil, to rise within the water accumulating in an upper layer in the interceptor. A fluid outlet from the grease interceptor is positioned below the level of the grease layer to permit substantially grease free wastewater to pass through the interceptor. In this way, the grease is collected in the grease interceptor and it may be periodically removed by direct bailing the grease out of the top of the grease interceptor. The grease is then' disposed of as solid waste in accordance with local regulations, for example, in dumpsters for removal to landfill sites.
Grease interceptors are typically installed below grade and in line with wastewater outlet or effluent pipes between where the kitchen is located and where the effluent pipe passes out of the building. A typical installation involves excavating a sufficiently large hole in the ground around a wastewater effluent pipe to permit the body of the grease interceptor to be placed in the hole, attached in line into the effluent pipe and to have a top of the interceptor at or above grade to permit the lid to be accessed for bailing. The excavated hole is then filled in around the grease interceptor and the floor is finished to the top edge of the grease interceptor. Ideally, the grease interceptor is installed in the ground with the upper edge being level with the floor grade and the inflow and outflow pipes connect directly to the inflow and outflow connectors of the grease interceptor in a manner to ensure proper operation of the wastewater through the interceptor.
However, a. problem with a typical installation is that, while the inflow and outflow pipe connectors on the body grease interceptor are provided at a predetermined height from the upper edge of the grease interceptor, there is no standard depth at which the wastewater pipes are located beneath the floor. Due to the need to provide a minimum slope to the pipe, and due to the position of the grease interceptor in any given pipe run being determined by what is convenient relative to the building layout, rather than how far away the sinks are, the connection to the waste water effluent pipe may be a various depths under the surface grade of the building. To preserve the wastewater gradient, in situations where the wastewater pipes are located deep below floor grade, it is common to install a grease interceptor with its upper edge positioned below floor grade, and then finish the floor to the upper edge of the grease interceptor with a downward slope from floor grade. This results in a dip in the finished floor where the grease interceptor is located which is generally aesthetically unappealing. Further it creates the tripping hazard of an uneven floor.
A further problem with conventional grease interceptors is that the cover is secured to the open top of the grease interceptor either by means of screw fasteners or quarter-turn fasteners which both have disadvantages. In the case of the screw fasteners a user must unscrew several screw-fasteners to remove the cover during periodic bailing which poses an inconvenience. While In the case of the quarter-turn fasteners the cover is more easily removed, there is another disadvantage in that the heads of the fasteners project upwardly from the floor and pose a tripping hazard or are liable to be bent or broken if stepped on.